Sarafian T A, Tsay K K, Jackson W E, Fluharty A L, Kihara H
Biochem Med. 1985 Jun;33(3):372-80. doi: 10.1016/0006-2944(85)90013-4.
Human liver arylsulfatase A was resolved into six fractions by narrow pH range preparative isoelectric focusing. Analytical isoelectric focusing revealed that most enzyme fractions were composed of two adjacent charge isomers. Nevertheless, there was considerable enrichment of charge species which allowed a comparative study of selected properties. Except for the most cationic fraction, neuraminidase treatment converted enzyme in all fractions to the three most cationic species. The most electronegative enzyme species had the highest molecular mass being made up of 64-kDa subunits. As electronegativity decreased, there was concomitant decrease in molecular mass and increase in complexity of subunit composition. Two subunits--61 and 55 kDa--prevailed with increasing proportions of the smaller unit with loss of electronegativity. There was also an increasing amount of a 26-kDa fraction which became a substantial component of the most cationic subfraction. Only enzyme in the two fractions containing the largest and most anionic species were taken up by cultured fibroblasts at higher efficiency than unfractionated enzyme. It is suggested that processing or maturation of arylsulfatase A incurs stepwise removal of charge groups and/or peptide segments leading to smaller, less-charged enzyme species.
通过窄pH范围制备性等电聚焦，人肝脏芳基硫酸酯酶A被分离成六个组分。分析性等电聚焦显示，大多数酶组分由两种相邻的电荷异构体组成。然而，电荷种类有相当程度的富集，这使得对选定性质进行比较研究成为可能。除了最具阳离子性的组分外，神经氨酸酶处理将所有组分中的酶转化为三种最具阳离子性的种类。电负性最强的酶种类具有最高的分子量，由64 kDa的亚基组成。随着电负性降低，分子量随之降低，亚基组成的复杂性增加。两种亚基——61 kDa和55 kDa——占主导地位，随着电负性的丧失，较小亚基的比例增加。还有越来越多的26 kDa组分，它成为最具阳离子性亚组分的重要组成部分。只有含有最大和最具阴离子性种类的两个组分中的酶被培养的成纤维细胞摄取的效率高于未分级的酶。有人提出，芳基硫酸酯酶A的加工或成熟会导致电荷基团和/或肽段的逐步去除，从而产生更小、电荷更少的酶种类。
